It has been claimed in the literature on English acquisition that children do not have the ability to use passive voice until about age 4 or 5. This is despite the fact that they control the morphology (the auxiliary verb be and the participial form of the verb) by this age. It has been claimed that the delay is due to the fact that children have a maturational delay (which is universal) which prevents them from connecting the patient role to the subject position in passives. For details see Horgan 1978, Maratsos, Fox, Becker and Chalkley 1985. Moreover, it has been claimed that under age 3 children do not generalize the construction, and therefore cannot extend it to nonce verbs if not exposed to a passive nonce frame (Brooks and Tomasello 1999), indicating that children under 3 have not formed an abstract and verb general passive construction. Passive is used as one of the main arguments that a certain number of verbs of a given type must be individually learned before the child can generalize a more abstract pattern.

In contrast to English, Indonesian passives are expressed without an auxiliary verb, by adding the prefix di- to the verb. For example, Gil (2004) has claimed that passives in Indonesian are very early, by age 2;06 or 2;08:

(4) Passive Indonesian:
ni tikus lagi dikejar sama kucing
this mouse more DI-chase with cat
“This mouse is being chased by a cat”

The passive voice is very frequent in Indonesian, much more frequent than in English. In English the frequency is estimated at about 4-5% in the input to children, but in Indonesian it is estimated between 28-35%.

We would like to investigate whether children (ages 2;00-5;00) can comprehend passive clauses easily in both English and Indonesian. If we find a difference between the two languages, one could then attribute the difference to morphology (by presumably claiming that passives in Indonesian are significantly ‘simpler'). We predict, however, that with the right comprehension methods passives in both English and Indonesian will be easily understood, undermining the maturational account. If comprehension is equivalent in both languages one can also argue against a frequency based analysis.